SHOCK ABSORBER FOR WASHING MACHINES, IN PARTICULAR HOUSEHOLD CLOTHES WASHING MACHINES

Abstract: Shock absorber for the oscillations of the unit tub-drum in household clothes washing machines. Shock absorber comprising a tubular housing (28) and a rod (33) reciprocatingly sliding therein, which are made with outlines of polygonal shape, having sides of number and form equal to each other, so as to coincide reciprocally at any shock absorber operative state, to allow the friction means (56) fixed to the rod (33) to exert always steady and evenly distributed braking actions on the tubular housing (28). The shock absorber is also made with removable and self-lubricating structure.

Description: SHOCK ABSORBER FOR WASHING MACHINES, IN PARTICULAR HOUSEHOLD CLOTHES WASHING MACHINES The invention relates to a shock absorber for wa¬ shing machines, and in particular for clothes wa¬ shing machines, adapted to support the units drum- tub of such machines and to dampen effectively the mechanical stresses produced during the operation of the machines referred to. Different kinds of shock absorbers for washing machines and in particular household clothes washing machines are known, adapted to support and dampen the mechanical stresses of the associated washing u- nits (tub and drum) of such machines during operation thereof, and connected between the lower portion of each washing unit and the lower base of the same ma¬ chines. These shock absorbers are generally formed by a hollow cylinder and a cylindric rod reciproca- tingly slidable inside such cylinder, which rod is provided with braking surfaces made of suitable material, co-operating with the inner surface of the cylinder, and which during operation of the respec¬ tive machine moves linearly and reciprocatingly insi- de the cylinder, due to the movements of the washing unit which are caused by the rotation of the drum at its different washing and centrifugating speeds, thereby producing a braking action adapted to dampen the generated mechanical stresses. These kinds of shock absorbers, which are generally made of metallic materials or sometimes also with component parts made of plastics, however, have so¬ me inconveniences above all when they must be fitted on clothes washing machines, whose drum is rotated with too high centrifugation speeds (higher than 1000 rpm) , in which conditions there are produced high me¬ chanical stresses by the washing unit on the machine structure. In fact, in such cases it has been found that on each shock absorber the rod slidable with a reciprocatingly rectilinear movement inside the cy¬ linder moves during its stroke also radially therein, so that the braking surfaces of such rod do not more exert braking actions distributed almost evenly on the entire cylinder inner surface, rather they exert irregular and variable braking actions on such inner surface, which tend to concentrate at pre-established positions of the same inner surface, thereby causing both premature and undesired wears and therefore a shorter life duration of each shock absorber and un¬ satisfying braking actions for the mechanical stres¬ ses of the washing unit. The present invention has the main object to elimi- nate the inconveniences associated to the use of the present shock absorbers, by means of a shock absorber of new kind adapted to ensure effective braking ac¬ tions distributed almost evenly on the same shock absorber, at any operative state of the clothes wa- shing machines, which is composed of simple component parts which can be assembled rapidly together and is able to operate for long life durations in a satisfy¬ ing and reliable way. The shock absorber according to the invention is made with the constructive characteristics substantially described with particular reference to the accompa¬ nying patent claims. The invention will be better understood by the follo¬ wing description, given solely by way of not limiting example, with reference to the enclosed drawings, wherein : - Fig. 1 shows schematically a washing machine pro¬ vided with at least a shock absorber according to the invention, - Figs. 2, 3 and 4 show, in respective front, side and exploded perspective views, a shock absorber ac¬ cording to the invention, - Fig. 5 shows schematically in a side view the two main component parts of the present shock absorber, inserted the one in the other one, - Figs. 6 and 7 show schematically in a front and side view the two main component parts of Fig. 5, ex- tracted the one from another, - Figs. 8, 9 and 10 show in plan views cut respecti¬ vely along the lines A-A, B-B and C-C the shock ab¬ sorber shown by Fig. 5, - Fig. 11 a, b, c shows a diagram of distribution of braking actions in a conventional shock absorber, - Fig. 12 a, b, c shows a diagram of distribution of braking actions in the present shock absorber, - Fig. 13 shows in a front view another component part of the shock absorber according to the invention, - Figs. 14 and 15 show the component part of Fig. 13 respectively cuts along the lines D-D and E-E, - Fig. 16 shows in a front view another component part of the shock absorber according to the inven- tion, - Fig. 17 shows the component part of Fig. 16 cuts along the line F-F. In Fig. 1 is represented schematically a washing ma¬ chine, in particular a household clothes washing ma- chine, marked with the reference numeral 20, compri¬ sing substantially a metallic box-like housing 21 in which a washing unit 22, formed by a washing tub 23 and a rotating drum 24 for containing the clothes, housed into the tub, is supported by means of upper suspension springs 25 and lower shock absorbers 26, fixed between the lower portion of the tub 23 and the lower base 27 of the machine housing, and provided for dampening the mechanical stresses caused by the washing unit swingings during drum operation at its washing and centrifugating speeds. In Figs. 2-7 is shown now schematically the one of the shock absorbers 26 according to the invention, which is constituted substantially by two main com- ponent parts, namely a metallic tubular housing 28 having elongated shape, which is internally hollow and provided respectively with an opened end portion 29 and a closed bottom portion 30, which is joined to an end zone 31 provided with a through hole 32 in which a rubber bush and thereafter a stud (both not shown) are inserted, for the articulated and vibra ¬ tion-damped connection thereof to the machine base 27, and by an elongated rectilinear rod 33 made of plastic material, which is so dimensioned as to be able to be inserted and adapted in the inner cavity 34 of the tubular housing 28, in such a way that to slide reciprocatingly and rectilinearly therein, the outer end zone 35 of which is provided with a thro- ugh hole 36, opposite to the hole 32 of the tubular housing 28, and in which there are inserted firstly a rubber bush and then a stud (both not shown) for the articulated and vibration-damped connection the¬ reof to the lower portion of the machine tub. As particularly evident from Figs. 2, 3, 4 and 8-10, the metallic tubular housing 28 is constituted by two half-shells 37 and 38 identical and symmetrical to each other, each one of which is shaped in the manner hereinafter described and is obtained by dra- wing and shearing processings of correspondent metal¬ lic sheet parts and are respectively provided with two rectilinear flattened edges 39 and 40, opposite to each other, adapted to be reciprocally aligned and overlapped and finally joined by means of resi- stance welding or per se known means. In particular, each half-shell is formed by an elon¬ gated rectilinear casing 41 having a polygonal sha¬ ped outline, with sides of equal or different sizes, which extends from the opened end portion 29 up to near the closed bottom portion 30, joined to the end zone 31, to which such rectilinear casing 41 is joi¬ ned with a set of tapered steps 42 and 43. In the present embodiment, each half-shell is shaped with a rhombus formed outer outline and is provided with a central flat side 44 and two adjacent flat and inclined sides 45 and 46, having almost the same size of the central side and inclinations symmetri- cally opposite to each other and directed from the correspondent edge of such central side 44 toward the longitudinal axis of symmetry A-A passing centrally in the tubular housing 28. Obviously, the shape and sides of the rectilinear casing 41 of each half-shell 37 and 38 may vary with respect to the present embo¬ diment, provided that there are always obtained flat sides which are able to perform the functions of dam¬ ping the oscillations of the washing unit of the wa¬ shing machines with the criteria hereinafter descri- bed. In turn, the elongated rectilinear rod 33 is preferably integrally made of molded plastic material and is constituted by two ribbed portions 47 and 48 joined together and shaped with an outer outline identical and having sizes slightly lesser than tho- se of the inner cavity 34 of the tubular housing 28, in order to be able to be adapted and to slide recti- linearly and reciprocatingly in the same housing, whe¬ rein said portions are provided with respective lon¬ gitudinal rectilinear ribs 49, 50 and 51, 52, joined orthogonally thereamong and extended respectively a- long the larger portion and the smaller one of the cross section of the tubular housing 28, said ribs be¬ ing delimited at their ends by plates 53, 54 and 55 having the same outline of said inner cavity 34, the plate 53 of which is larger than such inner cavity and is joined to the outer end zone 35 of the rod 33, and the plates 54 and 55 are slightly smaller than such inner cavity, in order to be able to slide the¬ rein, and are arranged respectively on a position in- terposed between the ribbed portions 47 and 48 and an end position of the rod 33, opposite to that whe¬ re the plate 53 is situated. In this way, when the rod 33 is inserted or extrac- 5 SUBSTITUTESHEET; RULt 6) ted with respect to the inner cavity 34 of the tubu ¬ lar housing 28, as evident from Figs. 5, 6 and 7, the plates 54 and 55 are exactly matched inside such tu ¬ bular housing, while on the contrary the plate 53 by abutting the free edge of said tubular housing pre ¬ vents said rod from being fully inserted into the sa¬ me tubular housing. Moreover, the ribbed portion 48, which is shorter than the remaining portion 47 of the elongated rec- tilinear rod 33, has the ribs dimensioned in such a way that to permit to house externally at least a friction pad 56 made of adequate antifriction mate¬ rial, adapted to exert a braking action by rubbing against the surface of the inner cavity 34 of the tubular housing 28, during the reciprocating movement of the rod 33 inside such tubular housing, caused by the oscillations of the tub-drum unit on the opera¬ tion of each machine, with consequent dampening of the mechanical stresses produced by such oscillations. In particular, the friction pad is ma¬ de with separated component parts each shaped like an elongated plate 59, provided with flat sides ha¬ ving the same outline and sizes slightly larger than the inner cavity 34 of the tubular housing 28, in or- der to permit such component parts to be adapted and to slide into said inner cavity. In the present case, the friction pad comprises two component parts 60 and 61, each one of which provided with two equal sides 62 and 63, inclined symmetrical - ly for the entire extent thereof, having the same in¬ clination of the correspondent adjacent sides 45 and 46 of the two half-shells 37 and 38 of the tubular housing 28. These friction pad elongated plates, evi¬ dent in detail also from Figs. 16 and 17, respective- ly in a front and a cut plan views, are provided with a plurality of through holes 64 distributed evenly on the surface thereof, so as to ensure the passage of the grease and other suitable lubricating materials therethrough, which are adapted to keep all the shock absorber component parts always lubricated during the operative cycles thereof, and which are housed externally against the rectilinear ribs 51, 52 of the ribbed portion 48 of the elongated rod 33, with the interposition of resilient elements shaped as two me¬ tallic flat springs 65 and 66, particularly evident from the Figs. 4, 8-10, each one of which is so di¬ mensioned and shaped as to be adapted with one sur- face thereof against the respective friction pad elongated plate and with the opposite surface thereof against the outer outline of the rectili¬ near ribs 51, 52 of said ribbed portion 48. Each metallic flat spring, in particular, is so sha- ped as to have one or more slots for the passage of grease or other suitable lubricating materials to keep the different shock absorber component parts al¬ ways lubricated, and in the present case such flat spring is shaped of rectangular form and comprises a central slot 67 along a longitudinal edge 68 thereof and two slots 69 and 70 along the other longitudinal edge 71 thereof, which slots are offset with respect to the previous one and in which a respective central lamina 72 and 73 is provided, which is bent with re- spect to the plane of the correspondent flat spring and turned toward the ribs 51, 52 of the ribbed por¬ tion 48, in order to act resiliently thereagainst in a way to urge therefore steadily each flat spring a- gainst the associated friction pad elongated plate, thereby by keeping it always pushed with a sliding contact against the surface of the inner cavity 34 of the tubular housing 28. By examining now the Figs. 11 and 12, shown therein are the diagrams of distribution of the braking for- ces respectively on a conventional shock absorber and a shock absorber according to the invention. By referring particularly to Fig. 11a, it is sche¬ matically shown a conventional cylindric shock absorber 74, comprising a cylindric rod 75 housed internally a cylindric box-like housing 76 and adap¬ ted to slide rectilinearly and reciprocatingly the¬ rein. In this case, the shock absorber is represen- ted at the rest state thereof, wherein the washing machine drum is still and therefore the rod 75 does not exert braking actions and may be practically considered in a coaxial relationship to the box-li¬ ke housing 76. In Fig. 11 b, on the contrary, in which is represented schematically the shock absor¬ ber at the operating state thereof, with the machi¬ ne drum puts into movement, it is noted that the rod 75 tends to move reciprocatingly in the box-li¬ ke housing 76 not only axially but also radially, thereby by arriving into contact with the inner sur¬ face of the same box-like housing, in this case on the zone marked with the reference numeral 77. Under this operative state, then, the rod 75 opera¬ tes eccentrically with respect to the box-like hou- sing 76 and therefore exerts irregular braking ac¬ tions against the inner surface of such box-like housing, namely which are greater at the contact zo¬ ne thereof and progressively decreasing from such zone on toward the remaining parts of said inner surface, as represented by a set of force vectors 78 in Fig. 11 c. By referring now to Fig. 12 a, it is shown schemati¬ cally a shock absorber 26 according to the present invention, at a rest state thereof, in which it is noted that the rod 33 is housed coaxially inside the tubular housing 28 and does not exert braking actions thereon. On the contrary, in Fig. 12 b where the shock absorber is represented at the operating state thereof, in which such rod is always shifted radial- ly thereby by sliding eccentrically inside the tubu¬ lar housing 28, it is noted that in this case the rod friction pad arranges itself with the surfaces of its two adjacent sides 62 and 63 against the cor- respondent sides 45 and 46 of the tubular housing 28, at the contact zone 77 thereof, so that the recipro¬ cating sliding of said friction pad into the tubular housing does not more exert, as previously, irregular braking actions against the inner surface of said tu¬ bular housing, rather it exerts steady and evenly distributed braking actions against such inner surface, thanks to the fact that the sides 62 and 63 of the friction pad are disposed always parallel to the opposite sides 45 and 46 of the tubular housing 28, both at the rest and operating state thereof, and therefore at this latter state in which the re¬ ciprocal rubbing of such sides at any contact posi¬ tion thereof is achieved, in correspondence of dif- ferent eccentricities between the rod and the tubu¬ lar housing, there are always produced braking ac¬ tions having the same intensity on the same sides, which are represented schematically in Fig. 12 c by a set of force vectors 78 having the same intensi- ty. In this way, the shock absorber according to the invention permits to obtain braking actions which a- re distributed almost evenly at any operative state of the washing machines, thanks to the fact that du¬ ring the operation of these machines the friction pad is steadily and evenly kept pressed against the tubular housing, by the flat springs 65 and 66, which for this purpose are advantageously made of harmonic steel, and so shaped as to be adapted tho¬ roughly to the outline of both the plates 59 of the friction pad and the ribs 51, 52 of the ribbed por¬ tion 48, thus providing on the one hand an effecti¬ ve and certain dampening of the mechanical stresses produced by the oscillations of the tub-drum unit during the drum movement, particularly at the high centrifugation speeds thereof, and on the other hand a reduced wear of such shock absorber and a longer life duration thereof. In addition, each shock absorber of this kind is sim- pie in its construction and formed by few component parts which can be assembled and disassembled rapi¬ dly and easily, which parts are made of metallic ma¬ terials and therefore permit the heat produced by the reciprocal friction of the same parts to be well disposed of. Finally, the presence of the ribs of the shock absorber ribbed portions 47 and 48, which are longitudinal to and directed on the same direc¬ tion of the mechanical stresses exerted by the wa- shing unit on the machine base, permits the shock ab¬ sorber to withstand effectively all the mechanical stresses of the washing unit, at both the rest and operative states thereof. Another important advantage obtained by the use of the present shock absorber is that to ensure always an effective and steady lubrication of the different component parts of the same shock absorber, thanks to the fact to provide, on the inner surface of the respective elongated rectilinear casing 41 of the two half-shells 37 and 38 of the tubular housing 28, a plurality of recesses 79 and 80, respectively ali¬ gned and inclined to each other with opposite incli¬ nation directions with respect to the longitudinal extent of such elongated casing (Fig. 2 shows a re- cess 79 cuts along the line G-G) . In this way, before each shock absorber be assembled on a washing machine, some grease or other suitable lubricating material is introduced therein, which therefore collects and concentrates itself in the re- cesses 79 and 80 and then is steadily drawn by the friction pad therefrom, during its reciprocating sliding in the tubular housing 28, and distributed on all the shock absorber component parts, by pas¬ sing through the through holes 64 of the plates of such friction pad and the recesses 67, 69 and 70 of the flat springs 65 and 66. In addition, each so obtained shock absorber permits the air contained inside it to be effectively vented during the reciprocating stroke of the rod 33 in the tubular housing 28, thanks to the presence of a plu¬ rality of through holes 81 provided on the two half- shells 37 and 38 of said tubular housing, and fore- seen in this case for the entire lenght of the respective central flat sides 44 of said half- shells. Finally, in accordance to the invention it is also possible to change the shape of the friction pad 56 and the tubular housing 28, by providing them with a polygonal form having a number of sides e- qual to each other and different to those previous¬ ly described solely by way of example, provided that the sides of such pad and the tubular housing are al¬ ways parallel and correspondent to each other at any washing machine operative state, and they can arrive always in contact together, by causing even and stea¬ dy braking actions at any contact position between said friction pad and tubular housing. 11

Claims: CLAIMS 1. Shock absorber for washing machines, in particular household clothes washing machines, adapted to be 5 fitted between the unit washing tub-drum and the lower base of the housing of these machines, in or¬ der to dampen the mechanical stresses produced du¬ ring the drum rotation at its different washing and centrifugating speeds, the shock absorber being for- 0 med by at least a tubular housing and a rod inser- table and slidable reciprocatingly into said tubu¬ lar housing, provided with friction means co-opera¬ ting with said tubular housing by friction action, so as to obtain braking actions adapted to dampen 5 said mechanical stresses, the shock absorber being moreover characterized in that said tubular housing (28) and said friction means (56) of said rod (33) are made removable and provided, at their zones of reciprocal frictional contact, with outlines of po- 0 lygonal shape having sides of number and form equal to each other, in a manner that the correspondent sides of said tubular housing (28) and said friction means (56) are coincident to each other at any ope¬ rative state, either of rest or operating state, of 5 the shock absorber, said friction means (56) being associated with resilient means (65, 66) adapted to keep them always into frictional contact with said tubular housing (28) . 2. Shock absorber according to claim 1, characterized 0 in that said tubular housing (28) comprises at least a first and a second separated metallic half-shell (37, 38), identical and symmetrical to each other, provided with rectilinear flattened edges (39, 40) adapted to be reciprocally adapted and joined in a 5 per se known manner, thereby providing an inner ca¬ vity (34) for inserting and sliding said rod (33) therein, said first and second half-shell (39, 40) being each constituted by an elongated rectilinear casing (41) whose outline is of polygonal shape, ha ¬ ving sides (44, 45, 46) with equal or different si¬ zes, extended from an opened end portion (29) the¬ reof, in which said rod (33) is inserted into said 5 inner cavity (34) , to a closed end portion (30) thereof adapted to be fixed to the washing machine. 3. Shock absorber according to claim 2, characterized in that said first and second half-shell (39, 40) are provided with a plurality of inner recesses 0 (79, 80) for accomodating some grease or other sui¬ table lubricating materials, and a plurality of through holes (81) for venting air contained inside them. 4. Shock absorber according to claim 3, characterized 5 in that said rod (33) is preferably integrally made of molded plastic material and is constituted by a first and a second ribbed portion (47, 48), joined together and shaped with an outer outline identical and having sizes slightly lesser than those of said 0 inner cavity (34) , as well as provided with respec¬ tive longitudinal rectilinear ribs (49, 50 ; 51, 52), delimited by plates (53, 54, 55) having the sa¬ me outline of said inner cavity (34) , the plate (53) of which is larger than said inner cavity (34) 5 and the plates (54, 55) are slightly smaller than the same inner cavity, in order to be able to sli¬ de therein. 5. Shock absorber according to claim 4, characterized in that said friction means (56) comprise a fric- 0 tion pad made of adequate antifriction material, provided with a first and a second separated com¬ ponent part (60, 61) shaped like an elongated pla¬ te (59) , each one of which is provided with sides (62, 63) coincident with those of said inner cavi- 5 ty (34) of said tubular housing (28) and co-opera¬ ting by friction therewith, each plate (59) being housed externally against said second ribbed por¬ tion (48) of said rod (33) , with the interposition 13 of said resilient means (65, 66) and being provi¬ ded with a plurality of through holes (64) into communication with said inner recesses (79, 80), for the passage of the grease or other suitable lu- bricating materials therebetween. 6. Shock absorber according to claim 5, characterized in that said resilient means comprise a first and a second metallic flat spring (65, 66) made of har¬ monic steel, which are so shaped as to be adapted to the outline of both the respective plates (59) and the correspondent ribs (51, 52) of said second ribbed portion (48) , said first and second flat spring (65, 66) being provided with respective la¬ mina (72, 73), bent with respect to the plane of the correspondent flat spring and turned toward said ribs (51, 52), in order to act resiliently thereagainst, and being also provided with slots (67, 69, 70) for the passage of grease or other suitable lubricating materials. 14 • 7: 01.n 'MΛ'

Inventors: FORNASARI LUCA, FORNASARI, LUCA
Applicants: R & D S SRL, R. & D.S. S.R.L.
Application year: 1994
Main classification: D06F37
IPC codes: D06F37, F16F7, F16F9